The present invention relates to travelling wire EDM apparatus in general, and more particularly to a method and mechanism for orienting the electrode wire support and guide members such as to effectuate in the workpiece a cut at an angle.
In travelling wire EDM apparatus, the electrode wire is held and guided between two guide member assemblies, one situated on one side and the other on the other side of the machining zone between the electrode wire and the workpiece. In order to effectuate in the workpiece an oblique cut, or a cut at an angle, the wire guide member assemblies, or wire guide "heads", are displaced transversely one relative to the other to cause the longitudinal axis of the wire to take a predetermined inclination which may be of several tens of degrees relative to a plane of reference. It is known that it is required to orient the machining fluid nozzle in the same direction as the wire guide heads to maintain an appropriate flow of machining fluid coaxially to the wire, and in order to avoid a machining error due to bending the wire as it exits and enters the respective guide heads.
The prior art contemplates several solutions to this problem. One solution consists in effecting a mechanical or electrical coupling between the transverse displacements of the wire guide head supports and the orientation of the wire guide heads relative to their supports (for example U.S. Pat. No. 4,431,896). The orientation of the two wire guide head supports may be synchronized by means of a pentograph (DBE No. 0084083) or by way of electric motors mounted on the wire guide head supports.
All the known solutions are complicated, and more particularly they are cumbersome which is particularly disadvantageous in view of the small room available proximate the wire guide heads.